Bringing a sextant back

To the editor: Last year I set out to locate a Plath sextant that could provide parts for my U.S. Navy MK 3 sextant. Daily watching of eBay finally produced a Plath that was not functioning according to the owner. Upon receiving the Plath it became immediately apparent that this instrument was too good to cannibalize even though the sextant looked like it had spent the night with the Samsonite luggage gorilla. The first order of business was to completely disassemble the sextant then soak the arc in ammonia. Scrubbing the arc with an old toothbrush removed all of the built-up corrosion. The mirrors and filters only needed a wipe down with alcohol. There was no way to save the 4-by-40-mm scope, so I removed the lenses to create a sight tube. The lighting system was also beyond repair.

Everything went back together as it came apart. Working the micrometer drum through the entire arc repeatedly with light oil helped to smooth out the operation of all the moving parts. A last touch was to strap on a digital watch to the sight tube with 24-hour GMT displayed. Finally I was off to the beach for calibration and testing. Observed LOP intercepts were within three nautical miles of GPS positions. This instrument has now become my traveling small craft sextant and sees more action than my other three sextants combined.